Are there any changes to the design which will better allow the survey to support model
development and testing?
The SAP thanked the Agency staff for their excellent presentations and the obvious level of effort that had gone into the proposal to date. The SAP noted that this was obviously a work in progress, and that the design needed considerable refinement. Because many issues require further clarification, the SAP noted that they would perhaps provide more questions than answers. The SAP supported the general goals of the design to: 1) obtain accurate estimates of chronic pesticide exposure in public drinking water systems using surface water sources, and 2) to collect information to develop and/or improve predictive models. However, the presentations implied that many other goals and objectives were being considered in the design. Hence, the details of the design remain too general for a full technical assessment of the approach. The likelihood of success will be dependent upon decisions that have not yet been explicitly made.
It was also unclear how this design may or may not relate or need to relate to considerations of studies to address acute exposure. The SAP was concerned that the level of funding being discussed may not be adequate. Also, there was strong consensus that the study design should not be dictated by an expected level of funding. An appropriate design should be considered and then a cost estimate would be constructed. The SAP noted that many of the sub-objectives need to be more clearly worked out so that the details of the design could be adequately addressed and reviewed.
The SAP also expressed concern that it was not clear how past studies and information had been used to guide the design. It was not evident if the extensive sampling programs of USGS and EPA had been used as "pilot" data to reach some of the design conclusions. Also, there was some concerns about details of the sample universe and some practical sampling issues. For example, it was noted that there were approximately 10,700 Community Water Systems (CWSs) using surface water that might constitute the sample population. The SAP noted that, from their knowledge, this figure must include purchased water systems that shouldn't be part of the sample. The sample universe is more likely about 5,500 system that use surface water as their source. This may make a difference in how the design is viewed. Also, is a CWS considered a single sample site? Many CWSs have multiple source intakes. Sampling the finished drinking water is typically done at the entry point to the distribution system; many systems have many entry points that may need to be sampled to characterize the finished water. Alternatively, would sampling from taps within the system be used to integrate samples. Such issues will affect the design and